1. Field of the Invention
The present invention relates to a battery power source device for supplying high electric power used for a drive power source for a vehicle.
2. Description of Related Art
Generally, the output of a rechargeable battery is from about 1 to 5 volts. When a high output voltage is necessary for an application such as a power source for the drive of a vehicle, a battery power source device which consists of a large number of rechargeable batteries 1 is required. These rechargeable batteries 1 are connected in series, and arranged in both lengthwise and widthwise directions within a battery box 2, as shown in a schematic longitudinal sectional view of FIG. 3. In this battery power source device, charge and discharge control is conducted so as to maintain the battery power source device in a state always capable of supplying a required level of electric power.
Since the temperature of the rechargeable battery 1 increases when it is charged and discharged, it is necessary for a battery power source device to provide cooling to limit such temperature increases. On the other hand, since temperature dependence of the internal resistance of the rechargeable battery 1 becomes very large when the rechargeable battery 1 is used in a place at low temperatures, differences in individual battery characteristics among the rechargeable batteries 1 become large if as much differences in temperature as they are at an ordinary temperature are present among the rechargeable batteries 1. As a consequence, overall control of the rechargeable batteries 1 is often prevented Thus, it becomes new to quickly increase the temperatures of the individual rechargeable batteries 1 to a temperature where any decrease of battery performance no longer remains a problem. Additionally, the temperatures of the rechargeable batteries 1 should be maintained at a uniform level when such a battery power source device, including a large number of the rechargeable batteries 1, is used at low temperatures. In addition, the dependency of the battery characteristics of each rechargeable battery 1 on temperature makes it necessary to maintain the temperatures of the entire arrangement of rechargeable batteries 1 at a uniform level.
Thus, controlling the temperatures of the individual rechargeable batteries 1 in a conventional battery power source device consists of adopting an arrangement for cooling the individual rechargeable batteries 1 by opening one end of the battery box 2 to form an air inlet opening 3, providing an air outlet passage 4 on the other end, and providing a fan 7 inside the air outlet passage 4 which is driven to blow air in one direction through the battery box 2, thereby forcing air E to flow between the individual rechargeable batteries 1. In addition, when the rechargeable batteries 1 are used at a low temperature, it is known to use a battery heater, such as a combustion heater or an electrical heater, installed on the battery box 2 so as to maintain the individual rechargeable batteries 1 at a predetermined temperature (such as one disclosed in Japanese Patent Laid-Open Publication No. Hei. 6-231807).
However, a problem with the temperature control described above is that, air E, having flowed from the air inlet opening 3, flows downstream while absorbing heat from the rechargeable batteries 1 when it passes between the rechargeable batteries 1, the temperature of the air E increases as it flows downstream. Thus, while the rechargeable batteries 1 on the side of the air inlet opening 3 are efficiently cooled by exchanging heat with the air E at a low temperature, he rechargeable batteries 1 on the side of the air outlet passage 4 are hardly cooled since they are exposed to the air E heated as a result of the heat exchange with the rechargeable batteries 1 on the upstream side. Consequently, the individual rechargeable batteries 1 are not uniformly cooled. As a result, there is such a problem that a large temperature difference is present between the rechargeable batteries 1 on the side of the air inlet opening 3 and the rechargeable batteries 1 on the side of the air outlet passage 4.
On the other hand, when the battery power source device is used at a low temperature, and the heater is installed to heat the rechargeable batteries 1 as described above, an independent cooler is necessary for use of the device at ordinary temperatures. Thus the structure becomes complicated, and as a consequence, the cost increases. As an alternative means for increasing the temperature of the rechargeable batteries without a heater, the rechargeable batteries are placed in a battery box in which a medium such as air does not flow, and the heat from the rechargeable batteries generated by charging and discharging is used to increase the temperature of the rechargeable batteries. However, in this method, since the heat generation varies among the individual rechargeable batteries due to variation in the internal resistance or the temperature characteristics among the rechargeable batteries or the heat dissipation varies among the rechargeable batteries due to the placement of the rechargeable batteries within the battery box, it is not possible to maintain the temperatures of the entire arrangement of rechargeable batteries at a uniform level.
The present invention has been devised in light of the above-described problems, and has an object of providing a battery power source device having a simple and inexpensive constitution which serves to cool batteries if the temperature is at ordinary temperatures, and quickly increase the battery temperature to a temperature range which does not decrease the battery performance while the temperatures of the individual batteries are maintained uniform if the temperature is low during use.
To achieve the object above, a battery power source device according to the present invention includes a battery box for storing a plurality of batteries arranged in a connected state in a battery storage room, an inlet opening for introducing a temperature control medium into the battery storage room, an outlet opening for discharging the medium from the battery storage room to the outside, a medium circulation passage for leading the medium discharged from the outlet opening to the inlet opening for feeding into the battery storage room again, and a medium transport device for forcing the medium flow.
If this battery power source device is used at low temperatures, since the temperature control medium, such as air, is introduced into the battery storage room again through the medium circulation passage for circulation after the medium has passed through the battery storage room, and consequently the temperature of the medium has increased due to heat exchange with the individual batteries, it is possible to quickly increase the temperatures of the individual batteries while the temperatures are maintained at a uniform level. In addition, if the battery power source device is used at ordinary temperatures, the individual batteries are cooled efficiently, and thus a proper temperature control effect is provided by discharging the temperature control medium outside from the outlet opening after the medium has flowed from the inlet opening and has passed through the battery storage room. Thus, though this battery power source device has a simple constitution which includes only the medium circulation passage without a heater or a cooler, it prevents a variation in the temperature characteristics of the individual batteries due to temperature unevenness of the batteries both at low temperatures and at ordinary temperatures. As a result, overall performance brought about by the entirety of batteries is maintained to a proper state.
It is preferable that the battery power source device further includes a selector valve mechanism for switching so as to selectively lead the temperature control medium discharged from the outlet opening either to an external outlet passage or the medium circulation passage, and a controller for controlling to switch the selector valve mechanism.
In the constitution described above, it is preferable that the controller includes a function for controlling switching of the medium transport device so as to reverse the flow direction of the medium in the battery power source device. It is preferable that the battery power source device further includes a temperature sensor for detecting the temperature of a battery in the battery storage room, or the temperature of the temperature control medium at a predetermined point in the battery storage room, and that the controller controls switching of the medium transport device in accordance with the temperature detected by the temperature sensor.
It is preferred that the battery power source device further includes another selector valve mechanism for switching so as to selectively a either the temperature control medium introduced from an inlet passages or the temperature control medium introduced from the medium circulation passage into the battery storage room, and that the controller control switching of the two selector valve mechanisms in conjunction with each other.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.